Fluid machine

ABSTRACT

A fluid machine includes a motor and a motor housing. The motor housing defines a motor chamber for accommodating the motor. The motor chamber is filled with inert gas. A rotor rotates in accordance with rotation of the motor. A pump housing defines a pump chamber for accommodating the rotor. A dividing wall is located between the pump housing and the motor housing. The pump housing and the motor housing are attached to each other via the dividing wall. Therefore, water is prevented from being generated in the motor chamber even if fluid that contains hydrogen leaks from the pump chamber to the motor chamber.

BACKGROUND OF THE INVENTION

The present invention relates to a fluid machine that draws fluid into apump chamber by rotation of a rotor and discharges the fluid out of thepump chamber through an outlet.

In a conventional fuel cell system that generates electric power usinghydrogen gas and oxidizing gas as reactive gas, water is produced duringgeneration of electric power. To discharge the generated water from thefuel cell, the hydrogen gas and the oxidizing gas are supplied to thefuel cell by an amount greater than a consumption amount required togenerate electric power. Therefore, the hydrogen gas discharged from thefuel cell (so called hydrogen off-gas) includes unreacted hydrogen gas.Discharging the unreacted hydrogen gas deteriorates fuel economy of thefuel cell system. Therefore, the hydrogen off-gas is circulated andreturned to the fuel cell to improve the fuel economy of the fuel cellsystem.

A fluid machine is used in the fuel cell system as means for forciblycirculating the hydrogen off-gas (see Japanese Laid-Open PatentPublication No. 2003-151592). That is, the fuel cell system of the abovepublication draws the hydrogen off-gas discharged from the fuel cell tothe fluid machine via a condenser, which separates gas from liquid. Themachine draws the hydrogen off-gas into a pump chamber and mixes thedrawn hydrogen off-gas with new hydrogen gas supplied from a hydrogentank. The hydrogen off-gas that is mixed with the new hydrogen gas issupplied to an anode of the fuel cell again. The ambient air, whichserves as the oxidizing gas, is supplied to a cathode of the fuel cellvia another fluid machine.

The fluid machine having such a function has been proposed in, forexample, Japanese Laid-Open Patent Publication No. 2002-54587. The fluidmachine of this Publication is an air pump that supplies air (oxidizinggas) to a fuel cell. The pump includes a motor housing and a pumphousing, which are integrally attached to each other. The motor housingdefines a motor chamber, which accommodates a motor. The pump housingdefines a pump chamber, which accommodates a rotor, which rotates inaccordance with rotation of the motor. The motor chamber and the pumpchamber are separated by a bottom wall (dividing wall) of the motorhousing through which a rotary shaft of the motor extends. A sealingmaterial is provided at a portion of the bottom wall where the rotaryshaft is inserted.

As described above, a fluid machine (hydrogen pump) for drawing hydrogengas (hydrogen off-gas) and supplying it to the fuel cell is provided inthe fuel cell system besides the fluid machine (air pump) for drawingair and supplying it to the fuel cell. In this case, the fluid machine(hydrogen pump) has substantially the same structure as the fluidmachine (air pump) disclosed in Japanese Patent Publication No.2002-54587 except that the fluid to be drawn and supplied is not air buthydrogen off-gas.

However, drawing and supplying hydrogen off-gas with the fluid machinedisclosed in Japanese Patent Publication No. 2002-54587 arises thefollowing problems. That is, since the hydrogen off-gas hascharacteristics to penetrate through metal, the hydrogen off-gas oftenpenetrates through the bottom wall (dividing wall) of the motor housing,which separates the pump chamber from the motor chamber, and enters themotor chamber. Although a sealing material is provided at a portion ofthe bottom wall of the motor housing where the rotary shaft of the motoris inserted through, a slight gap exists to permit the rotary shaft torotate. Therefore hydrogen off-gas moves from the pump chamber to themotor chamber through the slight gap.

In general, air is sealed in the motor chamber during assembly.Therefore, the oxygen contained in the air in the motor chamber and thehydrogen in the hydrogen off-gas that entered the motor chamber mightreact and generate water in the motor chamber. If water is generated asdescribed above, members (such as a motor) in the motor chamber might becorroded. As a result, the performance of the fluid machine mightdeteriorate.

SUMMARY OF THE INVENTION

Accordingly, it is an objective of the present invention to provide afluid machine that prevents water from being generated in a motorchamber even if fluid that contains hydrogen leaks from a pump chamberto the motor chamber, and prevents the performance of the fluid machinefrom deteriorating.

To achieve the above-mentioned objective, the present invention providesa fluid machine. The machine includes a motor and a motor housing. Themotor housing defines a motor chamber for accommodating the motor. Themotor chamber is filled with inert gas. A rotor rotates in accordancewith rotation of the motor. A pump housing defines a pump chamber foraccommodating the rotor. A dividing wall is located between the pumphousing and the motor housing. The pump housing and the motor housingare attached to each other via the dividing wall.

Other aspects and advantages of the invention will become apparent fromthe following description, taken in conjunction with the accompanyingdrawings, illustrating by way of example the principles of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with objects and advantages thereof, may best beunderstood by reference to the following description of the presentlypreferred embodiments together with the accompanying drawings in which:

FIG. 1 is a plan cross-sectional view illustrating a hydrogen pumpaccording to one embodiment of the present invention; and

FIG. 2 is a partially enlarged view of FIG. 1 explaining the state wherehydrogen off-gas enters the motor chamber of the pump shown in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

One embodiment of the present invention will now be described withreference to FIGS. 1 and 2.

FIG. 1 shows a hydrogen pump 10, which is one type of fluid machine usedin a fuel cell system. That is, the fluid machine in this embodiment isa fluid pump for fluid including hydrogen. The hydrogen pump 10 of thisembodiment is formed by a motor portion M and a pump portion P. Themotor portion M includes a substantially cup-shaped motor housing 11,which has a closed first end (left end in FIG. 1) and an open second end(right end in FIG. 1), and a partition (dividing member) 12, which iscoupled to the motor housing 11 to close the opening. The inner surfaceof the motor housing 11 and the inner surface of the partition 12 definea motor chamber 13. The motor chamber 13 is filled with inert gas (suchas nitrogen) G.

The pump portion P includes a substantially oval cup-shaped pump housing14, which has an open first end (left end in FIG. 1) and a bearing block(dividing member) 16, which is coupled to the pump housing 14 with bolts15 to close the opening. The inner surface of the pump housing 14 andthe inner surface of the bearing block 16 define a pump chamber 17. Inthis embodiment, the partition 12 and the bearing block 16 form adividing wall. The motor housing 11 is open toward the dividing wall andthe pump housing 14 is open toward the dividing wall. The dividing wallcloses the motor housing 11 and the pump housing 14.

A substantially oval cup-shaped gear housing 18 is secured to a secondend (right end in FIG. 1) of the pump housing 14 of the pump portion Pwith bolts (not shown). The gear housing 18 is smaller than the pumphousing 14. The outer surface of the second end of the pump housing 14and the inner surface of the gear housing 18 define a gear chamber 19.The outer surface of the partition 12 and the outer surface of thebearing block 16 are secured to each other with bolts (not shown) sothat the motor portion M is integrated with the pump portion P. AnO-ring 20 is arranged between the motor housing 11 and the partition 12,the pump housing 14 and the bearing block 16, the pump housing 14 andthe gear housing 18, and the partition 12 and the bearing block 16 as asealing member to keep the interior sealed from the outside.

A bearing 22 is located at a bottom portion 21 of the motor housing 11.The bearing 22 is coaxial with the motor housing 11 and faces theinterior of the motor chamber 13. The bearing 22 rotatably supports afirst end (left end in FIG. 1) of a drive shaft (rotary shaft) 23. Asecond end of the drive shaft 23 extends to the interior of the gearchamber 19 through a through hole 12 a formed in the partition 12, athrough hole 16 a formed in the bearing block 16, and a through hole 24a formed in a bottom portion 24 of the pump housing 14.

The second end of the drive shaft 23 is rotatably supported by a bearing25 located at the bottom portion 24 of the pump housing 14, and themiddle portion of the drive shaft 23 is rotatably supported by a bearing26 provided in the bearing block 16. A motor rotor 27 is secured to thedrive shaft 23 in the motor chamber 13. A motor stator 28 is secured tothe motor housing 11 such that the motor stator 28 is located on theouter circumferential side of the motor rotor 27. The motor rotor 27 andthe motor stator 28 form an electric motor 29.

A driven shaft 30, which is parallel to the drive shaft 23, is locatedin the pump chamber 17 of the pump portion P. The ends of the drivenshaft 30 are rotatably supported by a bearing 31 provided in the bottomportion 24 of the pump housing 14 and a bearing 32 provided in thebearing block 16. A two-blade drive rotor 33 and a two-blade drivenrotor 34 are secured to the drive shaft 23 and the driven shaft 30 inthe pump chamber 17, respectively. A second end (right end) of thedriven shaft 30 extends to the interior of the gear chamber 19 throughthe bottom portion 24 of the pump housing 14 in the same manner as thesecond end (right end) of the drive shaft 23. A drive gear 35 secured tothe second end of the drive shaft 23 and a driven gear 36 secured to thesecond end of the driven shaft 30 engage with each other in the gearchamber 19.

A seal ring (sealing material) 37 is located in the bearing block 16next to the bearing 26 on the side facing the drive rotor 33 to seal thegap between the drive shaft 23 and the bearing block 16. The seal ring37 is located between the inner surface of the through hole 16 a and thedrive shaft 23. In the same manner, a seal ring (sealing material) 37 islocated in the bearing block 16 next to the bearing 32 on the sidefacing the driven rotor 34 to seal the gap between the driven shaft 30and the bearing block 16. In this embodiment, a seal ring 37 is alsolocated in the bottom portion 24 of the pump housing 14 next to thebearing 25 on the side facing the drive rotor 33 to seal the gap betweenthe drive shaft 23 and the pump housing 14. In the same manner, a sealring (sealing material) 37 is located in the bottom portion 24 of thepump housing 14 next to the bearing 31 on the side facing the drivenrotor 34 to seal the gap between the driven shaft 30 and the pumphousing 14.

The hydrogen pump 10 is placed such that an imaginary plane thatincludes the axes of the drive shaft 23 and the driven shaft 30 ishorizontal. An inlet (not shown) is formed in the ceiling of the pumphousing 14 of the pump portion P to draw hydrogen off-gas dischargedfrom the fuel cell, which is not shown, into the pump chamber 17. Anoutlet 38 is formed in the bottom portion of the pump chamber 17 todischarge the hydrogen off-gas drawn by the rotation of the rotors 33,34 from the pump chamber 17. Therefore, the hydrogen off-gas drawn intothe pump chamber 17 from the inlet is discharged through the outlet 38and supplied to the fuel cell again. As described above, the hydrogenpump 10 repeats drawing and supplying operation in which hydrogenoff-gas is drawn into the pump chamber 17 and then discharged.

The operation of the hydrogen pump (fluid machine) 10 constituted asdescribed above will now be described. The operation performed whenhydrogen off-gas in the pump chamber 17 enters the motor chamber 13 willmainly be discussed below.

In a case where the hydrogen pump 10 repeats the drawing and supplyingoperation of hydrogen off-gas as described above, part of the hydrogenoff-gas drawn into the pump chamber 17 from the inlet might enter themotor chamber 13 via the through hole 16 a of the bearing block 16 andthe through hole 12 a of the partition 12 as shown in FIG. 2. That is,although the seal ring 37 is located in the through hole 16 a of thebearing block 16, a slight gap is formed between the seal ring 37 andthe drive shaft 23 to permit the drive shaft 23 to rotate.

A gap is also formed between the through hole 12 a of the partition 12and the circumferential surface of the drive shaft 23 to permit thedrive shaft 23 to rotate. Therefore, the hydrogen off-gas drawn into thepump chamber 17 might enter the motor chamber 13 through the gaps. Sincethe hydrogen gas (hydrogen off-gas) has the characteristics to penetratethrough metal, the hydrogen off-gas might penetrate through the bearingblock 16 and the partition 12, which are made of metal material (forexample, aluminum alloy), and enter the motor chamber 13.

However, in this embodiment, since the motor chamber 13 is filled withinert gas (nitrogen) G, that is, there is no residual air (oxidizinggas), the hydrogen off-gas that entered the motor chamber 13 does notgenerate water by a reaction with the air (oxidizing gas). Therefore,even if hydrogen off-gas enters the motor chamber 13, water is notgenerated by a reaction with air (oxidizing gas). Therefore, memberssuch as electric motor 29 in the motor chamber 13 are prevented fromcorroding. As a result, the performance of the hydrogen pump 10 isprevented from deteriorating.

The inert gas (nitrogen) G in the motor chamber 13 is prevented fromleaking into the pump chamber 17 by the seal ring 37 located in thethrough hole 16 a of the bearing block 16. The O-rings 20, whichfunction as the sealing members, prevent the inert gas (nitrogen) G fromleaking outside from the contact portion between the motor housing 11and the partition 12 and the contact portion between the partition 12and the bearing block 16 passing through the through hole 12 a of thepartition 12. The O-rings 20 further prevent water from entering themotor chamber 13 from the contact portion between the motor housing 11and the partition 12 and the contact portion between the partition 12and the bearing block 16.

The preferred embodiment has the following advantages.

(1) Even if hydrogen off-gas enters the motor chamber 13 from the pumpchamber 17, the motor chamber 13 is filled with inert gas (nitrogen) G,that is, there is no air (oxidizing gas). Therefore, water is notgenerated in the motor chamber 13 by a reaction between hydrogen andair. Accordingly, the members such as the electric motor 29 in the motorchamber 13 are prevented from being corroded by water, and theperformance of the hydrogen pump 10 is reliably prevented fromdeteriorating.

(2) Since the diffusion velocity of nitrogen that fills the motorchamber 13 as the inert gas G is slower (about ⅓) than that of the air,the nitrogen does not leak from the motor chamber 13 easily. Therefore,the performance of the hydrogen pump 10 is maintained for a long period.

(3) The sealing material, which is the seal ring 37 in this embodiment,is located in the through hole 16 a of the bearing block 16 throughwhich the drive shaft 23 extends. Therefore, the seal ring 37 reliablyprevents inert gas G in the motor chamber 13 from leaking into the pumpchamber 17 through where (through hole 16 a) the drive shaft 23 extendsin the bearing block 16.

(4) The sealing member, which is the O-ring 20 in this embodiment, islocated at the contact portion between the motor housing 11 and thepartition 12. Therefore, the inert gas G in the motor chamber 13 isreliably prevented from leaking outside from the contact portion betweenthe motor housing 11 and the partition 12. The O-ring 20 also preventswater from entering the motor chamber 13 via the contact portion fromthe outside.

(5) The sealing member, which is the O-ring 20 in this embodiment, islocated at the contact portion between the partition 12 and the bearingblock 16. Therefore, the inert gas G in the motor chamber 13 is reliablyprevented from leaking outside from the contact portion between thepartition 12 and the bearing block 16. The O-ring 20 also prevents waterfrom entering the motor chamber 13 via the contact portion from theoutside.

The invention may be embodied in the following forms.

In the preferred embodiment, the dividing wall is formed by thepartition (dividing member) 12, which closes the opening of the motorhousing 11, and the bearing block (dividing member) 16, which closes theopening of the pump housing 14. However, the dividing wall may be formedby only the bearing block 16. In this case, the bearing block 16 closesthe opening of the motor housing 11 and the opening of the pump housing14.

In the preferred embodiment, the O-ring 20 is used as the sealing memberlocated at the contact portion between the motor housing 11 and thepartition 12. However, the sealing member other than the O-ring 20 maybe used as long as the sealing member prevents inert gas G from leakingoutside via the contact portion and water from entering via the contactportion.

In the preferred embodiment, the sealing material, which is the sealring 37, is located in the through hole 16 a of the bearing block 16.However, the seal ring 37 may be located in the through hole 12 a of thepartition 12.

In the preferred embodiment, the motor chamber 13 is filled with theinert gas G, which is nitrogen. However, any inert gas other thannitrogen (for example, argon, helium, neon, xenon, and krypton) may beused as long as the inert gas does not react with hydrogen and generatewater. The motor chamber 13 may be filled with mixed gas (for example,nitrogen and neon) that is the mixture of several types of inert gasesG.

In the preferred embodiment, the present invention is embodied in thehydrogen pump 10, which circulates hydrogen gas (hydrogen off-gas) inthe fuel cell system. However, the present invention may be embodied inany fluid machine (hydrogen pump) other than that used in the fuel cellsystem as long as the fluid machine draws and supplies fluid thatincludes hydrogen.

The present examples and embodiments are to be considered asillustrative and not restrictive and the invention is not to be limitedto the details given herein, but may be modified within the scope andequivalence of the appended claims.

1. A fluid machine, comprising: a motor; a motor housing, which definesa motor chamber for accommodating the motor, the motor chamber beingfilled with inert gas; a rotor, which rotates in accordance withrotation of the motor; a pump housing, which defines a pump chamber foraccommodating the rotor; and a dividing wall located between the pumphousing and the motor housing, the pump housing and the motor housingbeing attached to each other via the dividing wall.
 2. The fluid machineaccording to claim 1, wherein the inert gas is at least one of nitrogen,argon, helium, neon, xenon, and krypton.
 3. The fluid machine accordingto claim 1, further comprising: a rotary shaft, which transmits rotationof the motor to the rotor, the dividing wall has a through hole throughwhich the rotary shaft extends; and a sealing material located betweenthe inner surface of the through hole and the rotary shaft.
 4. The fluidmachine according to claim 1, further comprising a sealing memberlocated at a contact portion between the motor housing and the dividingwall.
 5. The fluid machine according to claim 1, wherein the dividingwall includes a plurality of dividing members, which are piled on eachother, and a sealing member is located at least one of a portion betweenthe adjacent dividing members, a portion between the motor housing andthe adjacent dividing member, and a portion between the pump housing andthe adjacent dividing member.
 6. The fluid machine according to claim 1,wherein the motor housing is open toward the dividing wall and the pumphousing is open toward the dividing wall, wherein the dividing wallcloses the motor housing and the pump housing.
 7. The fluid machineaccording to claim 1, wherein the fluid machine is a fluid pump forfluid including hydrogen.
 8. The fluid machine according to claim 1,wherein the fluid machine is incorporated in a fuel cell system.
 9. Afluid machine, comprising: a motor; a motor housing, which defines amotor chamber for accommodating the motor, the motor chamber beingfilled with inert gas; a rotor, which rotates in accordance withrotation of the motor; a pump housing, which defines a pump chamber foraccommodating the rotor; a dividing wall located between the pumphousing and the motor housing, the pump housing and the motor housingbeing attached to each other via the dividing wall, and the motorhousing is open toward the dividing wall and the pump housing is opentoward the dividing wall, wherein the dividing wall closes the motorhousing and the pump housing; a rotary shaft, which transmits rotationof the motor to the rotor, the dividing wall has a through hole throughwhich the rotary shaft extends; and a sealing material located betweenthe inner surface of the through hole and the rotary shaft.